Liquid dispensing apparatus using a passive liquid metering method

ABSTRACT

A liquid dispensing device using a piezoelectric member in connection with an atomizing head and a passive metering method to supply liquid to the atomizing head. Preferably, the device is used to but not limited to dispensing of fragrances, insecticides or other aromatic solutions. The piezoelectric member does not vibrate the nozzle plate through which the liquid is dispensed. The passive metering method relies only on surface tension forces within the supply passageway. The device can work with a wider range of liquid properties than existing piezoelectric devices of this type. The passive metering method is robust and consistent, enabling larger and more varied liquid reservoirs because the reservoir height is not a factor in determining the performance of the device. The atomizing head functions with a wider range of liquids than atomizers whose nozzle plates are directly excited.

CROSS-REFERENCE AND INCORPORATION BY REFERENCE

This patent application claims the benefit of domestic priority of U.S.Provisional Application Ser. No. 61/073,275, filed Jun. 17, 2008, andentitled “Liquid Dispensing Apparatus Using A Passive Liquid MeteringMethod”. U.S. Provisional Application Ser. No. 61/073,275 is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The subject invention relates generally to liquid dispensing devicesand, more particularly, to liquid dispensing devices using piezoelectricactuation and passive metering methods.

BACKGROUND OF THE INVENTION

Devices exist to atomize and dispense liquids. These include liquiddispensers, medical devices, printing devices and many more. Pressurizedaerosol canisters and hand-operated sprayers are the most common devicesin use. Pressurized devices have environmental concerns related tovolatile emissions and are also limited by precision metering ofliquids, cost and power consumption.

Piezoelectric ultrasonic vaporization devices have been developed toincrease precision, especially for printing and medical deviceapplications. Some devices, such as used in a humidifier, are lessprecise and work only with certain types of liquids.

Other piezoelectric ultrasonic devices for liquid dispensing use avibrating membrane and a wick to deliver liquid to the vibratingmembrane. The wick limits the range of liquids to be used in thesedevices because of clogging of the wick and limitations of the viscosityof the liquid. The vertical orientation of a wick further restricts thedesign because it requires that the orientation of the vibratingmembrane be horizontal. Further, the vibrating membrane in such devicesis sensitive to residual accumulation of liquid on the plate. Thisreduces the range of liquids that can be used in such a device. Finally,the reservoir size that can be used in such a device is relativelysmall, because its height is limited by the height that a wick can drawliquid to the vibrating membrane.

Devices used to dispense ink for printing employ a chamber pressurizedfrom the back to eject droplets through a perforated membrane. Thesedesigns are appropriate for Inkjet printing but are relatively expensivebecause they require precise semiconductor fabrication processes. Insuch designs, the delivery of liquid to the perforated membrane is achallenge and only small volume reservoirs can be used.

SUMMARY OF THE INVENTION

The present invention is an improved device to atomize and dispenseliquids.

One embodiment of the present invention is focused on dispensingfragrances, perfumes, insecticides or other related aromatic solutions.

One embodiment of the present invention features an atomizing headconsisting of several plates forming a small chamber of liquid. Avibrating plate that is actuated by a piezoelectric device attached tothe vibrating plate compresses the chamber. The pressurized liquid isatomized as it is dispensed through a perforated membrane on the firstplanar member. The advantage of this design is that the device is lesssensitive to the liquid properties because it directly compresses liquidin the chamber. This is an advantage compared to devices that directlyvibrate the perforated membrane plate, which are more sensitive becausethey rely on liquid inertia to propel the liquid and therefore depend onthe liquid properties, especially including viscosity and specificgravity.

One embodiment of the present invention incorporates a new method fordelivering liquid to the atomizer head. The device consists of a largeliquid reservoir with a downward-pointing tube. The tube allows liquidto fall into a small liquid reservoir. An air lock between the liquidlevel in the small reservoir and the tube automatically maintains thedesired liquid height in the small reservoir and the tube automaticallymaintains the desired liquid height in the small reservoir. Surfacetension forces draw the liquid from the small reservoir automatically tothe atomizer head with a controlled backpressure. This system providespassive metering of liquid to the atomizing head and is passive, simpleand low-cost. Another advantage of this design is that there is norestriction on the size of the large reservoir.

This embodiment of the present invention requires no pressurized gaspropellant (VOC's), which are increasingly regulated by both State andFederal Agencies, thereby eliminating environmental challengesassociated with such aerosol devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the illustrated embodiment of the invention, which arenovel, are described in detail herein below. The organization and mannerof the structure and operation of the invention, together with furtherobjects and advantages thereof, may best be understood by reference tothe following description and viewed in connection with the accompanyingdrawings wherein like reference numerals identify like elements inwhich:

FIG. 1 shows a device for dispensing atomized liquid. The exteriorhousing 1 preferably is a plastic injection-molded part that serves as ahousing for the internal components, a mounting structure, and includesthe desirable external shape features for the liquid dispensingapparatus 5 and tube 5′. The exterior housing incorporates a controlprinted circuit board (PCB) 2. The large liquid reservoir 3 is mountedinside the exterior housing 1. The exterior housing also contains apower supply, preferably two AA-cell, C-cell or D-cell batteries 4.

FIG. 2 is an exploded view of the liquid dispensing apparatus 5. Theexploded view shows the large liquid reservoir 3, located adjacent tothe liquid dispensing apparatus 5, which supplies liquid to the smallerreservoir 7. The atomizing head 6 is seated in the assembly via a springloading of the atomizing head's planar members.

FIG. 3 shows a side-view cross section of the liquid dispensingapparatus 5. The second reservoir 7 maintains a supply of liquid that isdelivered to an atomizing head 6. The tube 5′ provides a pathway for theliquid to flow from the large liquid reservoir 3 to the smallerreservoir 7. The bottom edge of the tube 5′ limits the liquid level sothe atomizing head 6 is supplied with a constant liquid level. Thegeometry formed by the planar features of the atomizing head 6 and thecurved tube 5′ outer surface provides a means for the surface tensionforces to deliver liquid from the small reservoir 7 to the chamber inthe atomizing head 6.

FIG. 3 a shows a side-view cross section of the liquid dispensingapparatus 5 and the atomizing head 6.

FIG. 4 shows a close-up exploded view of the atomizing head 6. Theatomizing head 6 comprises several planar members and other componentsthat are affixed to each other, preferably using a solder-bond process.As illustrated, a first planar member 8 is a cylindrical plate. Thefirst planar member 8 includes an aperture plate 9, which containsnozzle-shaped holes 13. For purposes of explanation only, once affixed,the aperture plate 9 is then considered an integral part of the firstplanar member 8. The first planar member 8 is affixed to a spacer plate10. The spacer plate 10 also serves to prescribe the axial distancebetween the first planar member 8 and a second planar member 11. Theatomizing head assembly provides a means for rigidly supporting the thinaperture plate 9, a resonant actuator for pumping the liquid, and aliquid cavity from which to dispense liquid. A notch 14 at the bottomedge of the hole located in the spacer plate 10 provides a portion ofthe pathway for the liquid to be drawn into the liquid cavity. Apiezoelectric ring 12 is affixed to the back of the second planar member11.

FIG. 5 shows a close-up cross section view of tapered holes 13 in theaperture plate 9. The tapered apertures 13 are a series of holes thatprovide a means for the liquid particles to be atomized and projectedthrough the first planar member 8.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For purposes of the description hereinafter, the words “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”,“longitudinal”, “small”, “large” and like spatial terms, if used, shallrelate to the described embodiments as oriented in the figures. However,it is to be understood that many alternative variations and embodimentsmay be assumed except where expressly specified to the contrary. It isalso to be understood that the specific devices and embodimentsillustrated in the accompanying drawings and described herein are simplyexemplary embodiments of the invention.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. The presentlypreferred embodiments described herein are meant to be illustrative onlyand not limiting as to the scope of the invention which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof. For example, while the present invention is implementedprimarily from the point of view of dispensing liquids containingliquids in the described embodiments, the present invention may also beeffectively implemented on, for example, but not so limited to,printing, chemical dispersion on production lines, etc.

The present invention vaporizes and dispenses liquid without the use ofcompressed gas propellants, achieving environmental benefits. Thepresent invention is more robust in its liquid delivery method comparedto ultrasonic piezoelectric devices employing wicks. Accordingly, thedevice can work with a wider range of liquid properties than existingpiezoelectric devices of this type. The passive metering function isrobust and consistent, enabling larger and more varied liquid reservoirsbecause the reservoir height is not a factor in determining theperformance of the device. The atomizer head with a chamber excited onits second planer member functions with a wider range of liquids thanatomizers whose membrane plate is directly excited.

FIG. 1 is an image of a preferred embodiment of the present invention.The exterior housing 1 is preferably a plastic injection-molded partthat serves as a housing for the internal components, a mountingstructure, and includes the external shape features for the liquiddispensing apparatus. The exterior housing incorporates a printedcircuit board (PCB) 2. The PCB performs computations and provides aninterface to the user controls that can allow for changes to the timeand duration of the duty cycle for dispensing the liquid, which may ormay not be co-located on the backside of the PCB, accessible through theexterior housings via depressible buttons, switches or other controls.The PCB 2 contains a signal generator module that generates a specificoscillating voltage signal to excite the piezoelectric liquid dispensingapparatus. The PCB also contains power amplifier components to amplifythe signal to the appropriate voltage and current necessary to drive thepiezoelectric atomizing device, all of which circuitry is well known inthe art. In some embodiments, the invention may comprise several printedcircuit boards electrically connected via wires to perform the neededfunctions. A liquid reservoir 3 is mounted inside the exterior housing1. The liquid reservoir contains the liquid or other liquid to bedispensed into the air by the device. It should be noted that the liquidreservoir 3 is not a pressure vessel and is not pressurized withpropellant, differentiating it from aerosol reservoirs. The liquidreservoir 3 is equipped with an outlet fitting 3′ that is scaled duringshipping with a seal made of foil, plastic film, cap or other material.During replacement of a liquid reservoir, it is oriented such that theoutlet fitting 3′ faces downward and is inserted onto a tube 5′,providing a seal between the reservoir 3 and the tube 5′ and providing apath for liquid to flow into the second reservoir 7 (see FIG. 2). Theexterior housing 1 also contains a power supply, preferably two AA-cell,C-cell or D-cell batteries 4.

FIG. 2 is an exploded view of the liquid dispensing apparatus 5. Thebottom of the liquid reservoir 3 is shown in its orientation duringinstallation and during use. The tube 5′ of the liquid dispensingapparatus 5 penetrates the seal of the large liquid reservoir 3 duringreplacement or installation. The large liquid reservoir 3 has low gaspermeability to air. Upon installation, the large reservoir 3 isconnected with the tube 5′ to provide an airtight seal. The largereservoir 3 must be sufficiently rigid so that it will not deform frompressure changes while the device is in operation. This allows liquid tofeed via gravity into a second, smaller reservoir 7. The liquid level ofthe second reservoir 7 is automatically and passively controlled withpressure forces created by the pressure within the second reservoir 7once the liquid level of the second reservoir 7 fills to a level thatprevents the passage of air into the tube 5′ and liquid reservoir 3 asbest understood with reference to FIG. 3. During operation, liquid isdrawn out of the second reservoir 7, lowering its level. When the leveldrops to the point where the liquid level is below the bottom of thetube 5′, air enters the liquid reservoir 3 and additional liquid movesvia gravity forces from the liquid reservoir 3 into the second reservoir7. This process fills the second reservoir 7 until the level is onceagain equal to or higher than the bottom edge of the tube 5′, sealingoff the flow of air and achieving a new pressure equilibrium. Thisprocess occurs automatically until the liquid reservoir 3 is emptied ofits liquid. An essential feature of this operation is that the level ofthe liquid in the second reservoir 7 is maintained with only a smallfluctuation. This enables a near-constant supply of liquid to bedelivered to the atomizing head 6 at a constantly maintained level andpressure, which is important with respect to preventing unwanted leakagethrough the atomizing head, as will be more fully understood uponreading the discussion below.

FIG. 3 shows a side-view cross section of the liquid dispensingapparatus 5. The second reservoir 7 maintains a supply of liquid that isdelivered to an atomizing head 6. The liquid level in the secondreservoir 7 is maintained at or very near to the height of the bottom ofthe tube 5′. Liquid is passively delivered upward from the bottom edgeof the spacer plate 10 to the upper region of the atomizing head 6 byway of surface tension forces. Surface tension in the liquid that isresponsible for transporting the liquid upward against the force ofgravity is established by the geometry formed between the back side ofthe planar atomizing head spacer plate 10 and the curved exteriorsurface of the tube 5′.

FIG. 3 a shows a side-view cross section of the liquid dispensingapparatus 5 and the atomizing head 6. The liquid that is drawn upward bysurface tension in the region between the planar spacer plate 10 and thecurved exterior surface of the tube 5′ is further drawn upward from thebottom circumferential edge of the second planar member and into theliquid chamber via a small opening at the bottom of the liquid chamber.The opening is defined by a notch 14 (see FIG. 4) at the bottom edge ofthe hole in the spacer plate 10 and the first and second planar members.The passage defined by the exterior surface of tube 5′ and theparticular geometry in the atomizing head 6 enables liquid to reach theapertures 13 in the atomizing head 6 without the need for a capillarytube or wick.

FIG. 4 shows a close-up exploded view of the atomizing head 6. Theatomizing head consists of several planar members and other componentsthat are affixed to each other, preferably using a solder-bond process.The planar members can also be affixed together using laser or spotwelding, sheet metal forming of one or more planar members, oradditional parts including a plastic housing. A first planar member 8 ispreferably a cylindrical plate made of stainless steel or brass,depending on the liquid application. The first planar member 8 includesan aperture plate 9, which contains preferably 10 to 200 nozzle-shapedholes. The holes are tapered from the back to the front of the apertureplate and are preferably sized between 5 to 20 um in diameter at theirsmallest dimension. The aperture plate 9 is fabricated preferably usingan electro forming process with a nickel alloy or other metal compatiblewith the electro forming process. The aperture can also be fabricatedusing a laser abolition process. Its size and shape are tailored tominimize production costs. Once affixed, the aperture plate 9 isconsidered for purposes of this discussion to be an integral part of thefirst planar member 8. The first planar member 8 is affixed to a spacerplate 10. The base of the spacer plate serves as the base of theatomizing head 6. The spacer plate 10 also serves to prescribe the axialdistance between the first planar member 8 and a second planar member11. This distance is important to the structural vibration and fluiddynamics of the device, and is preferably between 25 and 100 um. Thesecond planar member 11 (also sometimes referred to as the resonatorplate) is affixed to the back of the spacer plate 10. Once assembledwith the first and second planar members, together with the circularhole in the spacer plate 10 forms a very small chamber from which avolume of liquid is dispensed. The liquid drawn up to the upper regionof the atomizing head 6 using surface tension enters the small liquidchamber through an opening formed by a notch 14 at the bottom edge ofthe hole in the spacer plate 10. A piezoelectric ring 12 is affixed tothe back of the second planar member 11. This piezoelectric ring ispreferably solder bonded to the second planar member with a lowtemperature solder so as to not depole the piezoelectric material. Thepiezoelectric material is poled along the symmetric axis of thepiezoelectric ring. The voltage is applied between an electrode on theback surface of the piezoelectric ring and the electrically conductivesecond planar member. Voltage with the same sense as the piezoelectricpoling direction generates an electric field in the piezoelectricmaterial such that the piezoelectric ring contracts radially andcircumferentially, but extends axially. Voltage with an opposite senseto that of the poling direction will generate an inverse deflection inthe piezoelectric material. Piezoelectric coupling in this configurationis characterized by the d₃₁ constant. During operation, oscillatingvoltage is applied to the piezoelectric ring, causing it to oscillate atthe corresponding frequency. These contractions and expansions result inan oscillating stress at the interface between the piezoelectric ringand the second planar member 11. The oscillating stress createsvibrations of the second planar member 11 at a frequency correspondingto its structural resonance. This creates amplified vibrations, whichgenerate oscillating pressure in the small volume of liquid between thefirst and second planar members. The combination of motion and pressureatomizes the liquid as it passes through the apertures 13 in the firstplanar member 8, and provides the liquid with sufficient velocity suchthat it is ejected from the atomizer head 6 in a direction normal to thesurface of the first planar member such that it travels a sufficientdistance from the external housing 1. Traveling a sufficient distanceprevents liquid from landing on the external housing 1, and, in the caseof fragrance, improves the dispersion of the fragrance through the air.In a preferred embodiment of the atomizer head 6, the region in whichthe first planar member 8 is located is oriented at an angle such thatthe vector defined by the liquid ejection relative to a horizontal plateforms a 0 to 60 degree angle. Changing the orientation of the entireatomizer head 6, or introducing a bend in the spacer plate 10 at alocation below the first planar member 8 can achieve this. An additionalfeature of the embodiment of the invention is that it allows forlong-term or constant operation of the liquid dispenser. This isachieved because the atomization is robust and does not depend onformation of a film or residue of liquid on the first planar member 8,as is the case in devices of the prior art.

FIG. 5 shows a close-up cross section view of tapered holes 13 formed inthe aperture plate 9. The structure of the aperture plate 9 is shownshaded. The tapered apertures 13 are a series of holes that provide ameans for the liquid particles to be atomized and projected through thefirst planar member 8.

While preferred embodiments of the present invention are shown anddescribed, it is envisioned that those skilled in the art may devisevarious modifications of the present invention without departing fromthe spirit and scope of the appended claims.

1. An atomizing head for use in a liquid dispensing device, saidatomizing head comprising: first and second members which each havefront and rear planar surfaces, said first member has an aperture whichextends therethrough from said front planar surface thereof to said rearplanar surface thereof; at least one nozzle associated with said firstmember for dispersing liquid; a piezoelectric member affixed to saidrear planar surface of said second member; a first plate having frontand rear planar surfaces, said front planar surface of said first platebeing affixed to said rear planar surface of said first member, saidrear planar surface of said first plate being affixed to said frontsurface of said second member, said first plate defining an aperturetherethough, said aperture of said first plate defining a liquid chamberwhich is defined between said first and second members, said at leastone nozzle being in fluid communication with said liquid chamber; and asecond plate having front and rear surfaces, said second plate having atleast one hole which extends therethrough from said front surface tosaid rear surface, said front surface of said second plate being affixedto said rear planar surface of said first member in such a manner thatsaid at least one hole defined by said second plate is in fluidcommunication with said aperture defined by said first member, said atleast one hole of said second plate defining said at least one nozzleassociated with said first member, said second plate being positionedwithin said aperture of said first plate and further defining saidliquid chamber.
 2. The atomizing bead as defined in claim 1, whereinsaid second plate has approximately 10 to 200 holes extendingtherethrough.
 3. The atomizing head as defined in claim 1, wherein saidat least one hole extending through said second plate has a smallestdiameter of approximately 5 to 20 um.
 4. The atomizing head as definedin claim 1, wherein said first member is a cylindrical plate.
 5. Theatomizing head as defined in claim 1, wherein said first plate definesan axial distance between said first member and said second member. 6.The atomizing head as defined in claim 5, wherein said axial distancebetween said first member and said second member is approximately 25 to100 um.
 7. The atomizing head as defined in claim 1, wherein saidaperture provided through said first plate is generally circular inconfiguration.
 8. The atomizing head as defined in claim 1, wherein saidaperture provided through said first plate defines a notch at a lowerend thereof, said notch being positioned below said first and secondmembers in order to allow liquid to enter said liquid chamber via saidnotch.
 9. The atomizing head as defined in claim 1, wherein said secondmember is a solid cylindrical plate.
 10. The atomizing head as definedin claim 1, wherein said piezoelectric member is in the shape of a ring.11. The atomizing head as defined in claim 1, wherein said nozzles aretapered in configuration.
 12. An atomizing head for use in a liquiddispensing device, said atomizing head comprising: a first member havinga front surface and a rear planar surface, the first member defining anaperture which extends therethrough from the front surface to the rearplanar surface; a second member having a front planar surface and a rearsurface; a spacer member having front and rear planar surfaces, thespacer member being positioned between the first and second members withthe front planar surface of the spacer member being affixed to the rearplanar surface of the first member and with the rear planar surface ofthe spacer member being affixed to the front planar surface of thesecond member, the spacer member defining an aperture which extendstherethrough from the front planar surface thereof to the rear planarsurface thereof, the aperture of the spacer member defining a liquidchamber which is defined between the rear planar surface of the firstmember and the front planar surface of the second member; apiezoelectric member affixed to the rear surface of the second member;and a plate member having a front planar surface and a rear surface, thefront planar surface of the plate member being affixed to the rearplanar surface of the first member and being sized to cover the aperturedefined by the first member, the plate member being wholly positionedwithin the liquid chamber defined by the aperture of the spacer member,the rear surface of the plate member being separated from the frontplanar surface of the second member, the plate member defining at leastone nozzle-shaped hole which extends therethrough from the front planarsurface thereof to the rear surface thereof, the at least onenozzle-shaped hole of the plate member being in fluid communication withboth the aperture of the first member and the liquid chamber, wherebyactivation of the piezoelectric member causes the second member tovibrate, thereby generating oscillating motion and pressure in liquidcontained in the liquid chamber and causing the liquid to be atomizedand dispersed through the at least one nozzle-shaped hole, through theaperture of the first member and outward beyond the front surface of thefirst member.
 13. The atomizing head as defined in claim 12, wherein thefront surface of the first member is planar.
 14. The atomizing head asdefined in claim 12, wherein the rear surface of the second member isplanar.
 15. The atomizing head as defined in claim 12, wherein the rearsurface of the plate member is planar.
 16. The atomizing head as definedin claim 12, wherein an axial distance between the front planar surfaceof the plate member and the rear surface of the plate member is between25 and 100 um.
 17. The atomizing head as defined in claim 12, whereinthe at least one nozzle-shaped hole is tapered from the rear surface ofthe plate member to the front planar surface of the plate member. 18.The atomizing head as defined in claim 12, wherein the at least onenozzle-shaped hole has a minimum diameter of between 5 and 20 um. 19.The atomizing head as defined in claim 12, wherein the plate member hasapproximately 10 to 200 nozzle-shaped holes extending therethrough. 20.The atomizing head as defined in claim 12, wherein the piezoelectricmember is in the shape of a ring.
 21. The atomizing head as defined inclaim 12, wherein the atomization and dispersion of the liquid throughthe at least one nozzle-shaped hole is not caused by a significantvolume change of the liquid chamber.
 22. The atomizing head as definedin claim 12, wherein the second member is formed of an electricallyconductive material such that the second member vibrates when thepiezoelectric member is vibrated.
 23. The atomizing head as defined inclaim 12, wherein the spacer member further has a delivery passagewayprovided therein for providing liquid to the liquid chamber, the liquidchamber being located above the delivery passageway.
 24. The atomizinghead as defined in claim 12, wherein the first member is a cylindricalplate.
 25. The atomizing head as defined in claim 12, wherein theaperture provided through the spacer member is generally circular inconfiguration.
 26. The atomizing head as defined in claim 12, whereinthe aperture provided through the spacer member defines a notch at alower end thereof, the notch being positioned below the first and secondmembers in order to allow liquid to enter the liquid chamber via thenotch.
 27. The atomizing head as defined in claim 12, wherein the secondmember is a solid cylindrical plate.